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Any help is much appreciated

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by Caleb, Sep 13, 2014.

  1. Caleb

    Caleb Iron Registered Member

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    First, let me say that I'm going to say some really stupid things since I'm a beginner. I apologize in advance, and thank you for any help you can provide.

    I'm trying to make some titanium wedding rings.

    I've got a small 7x12'' Grizzly lathe (tried to find a southbend locally, without success).

    I was finally able to cut a piece off yesterday, after I flipped my tool the right side up..

    So now that I've got a little experience with the parting bit, I'm trying to bore the interior of the ring, so I can set it up for boring tools. I haven't had any success, and the lathe keeps stopping, which leads me to believe I'm doing something really wrong.

    I'm running the lathe at about 150 rpms, and pushing the tool in about .025 mm every few seconds. Is there something I should change?

    Any help you can provide is much appreciated.
     
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  2. JimDawson

    JimDawson Global Moderator Staff Member Director

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    Don't worry about asking questions, we're here to help out where we can. We were all inexperienced when we started out.

    A picture of your setup would be helpful in this case.

    From your description, I assume you parted off the blank, mounted it in the chuck, and then are drilling it to start the boring process. I'm not sure why it is requiring so much power to do this operation, however, you are starting out with some pretty tough material. Maybe you are trying to take a much too heavy cut. You might try this with a piece of steel or aluminum first just to get the technique down.

    In general, if I were making a ring, I would drill then bore the interior first, do the exterior features, then part off the work. That way you don't have to part through the the entire thickness of the material, and you don't have to worry about crushing the ring while holding it in the chuck.

    I hope this helps.
     
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  3. Caleb

    Caleb Iron Registered Member

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    Thanks Jim.

    Here's what I'm working with: http://imgur.com/a/sgFxb

    Figured out yesterday that my tool was flipped upside down.

    I'm starting again, so that piece on the end is scrap. So I'm trying to bore the end of the barstock now.

    I ordered a carbide parting tool, so hopefully it will be easier next time compared to the HSS (less fire).

    Maybe I need some different endmill bits to work with? They are titanium nitride, and don't seem to be putting up with what I'm putting them through. That or I'm probably moving too fast, or at the wrong speed
     
  4. richl

    richl United States Active User Active Member

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    Drill bits are a nice way to get a hole started for boring. They are cheap, clean and efficient, but they require a drill chuck that slides into your tailstock. I have never worked titanium though so i might not be giving you the best answer.
    Looks like you are working on a cool project though, good luck!

    Rich
     
  5. JimDawson

    JimDawson Global Moderator Staff Member Director

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    OK, I think I understand part of the problem, titanium nitride does not work when cutting titanium, the titanium tends to weld to the tool bit. If I understand correctly, you are using an endmill to drill the hole. If you want to use an endmill to size the hole, that is OK, but I would drill a pilot hole first. Endmills don't do to well as a drill bit.

    The other thing that I see is that you have a lot of overhang in your setup, both the parting tool and the work piece. Try working closer to the chuck and shortening up the parting tool. I'm not sure of the spindle speed for titanium. You may be feeding too slow, titanium tends to work harden at a drop of the hat. This may be helpful http://www.supraalloys.com/technical-speedfeed.php

    I would drill the hole in the bar stock to near the finished size then finish the bore with a boring bar. I think a cobalt drill bit will work in titanium.
     
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  6. Caleb

    Caleb Iron Registered Member

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    That clears a lot up. The titanium nitride bits seemed to work for a few mm, then they were pretty much junk. I'm definitely going to get some cobalt bits, thanks for the suggestion.

    Also, I was lingering too long with the bit, and I must have been hardening the surface by doing that. I think I was actually going too slow.

    I tried to cut the bar stock down, so I could get the entire piece closer to the chuck, but I'll have to wait for the carbide parting tool to get here. The HSS is definitely shot.

    Thanks again for your help Jim
     
  7. JimDawson

    JimDawson Global Moderator Staff Member Director

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    Just grind the HHS bit back past the dull area. Don't let it get too hot while grinding, keep a cup of water handy to dip it in as you grind it. If you don't have a bench grinder, it's time to put one on your wish list. You always need a new tool anyway, you can never have too many tools. :whistle:
     
  8. DMS

    DMS United States Active User Active Member

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    I don't think you will be able to drill to full diameter on that lathe, in that material. If you can try getting it to 0.5", then boring the rest of the way, you will have better luck. I think the problem with stalling is due to the stickout. The 7x series of lathes is capable, but you must respect it's limitations. Even on a larger machine, the rule is to have the absolute minimum of overhang on both work and tooling that you can get away with. I also agree with Jim, finish the inside, outside, and exposed edge before parting off, flipping around, and doing the final finish.

    You may also think about getting some cheaper material to experiment with. Stainless steel is very similar to titanium with respect to machinability, and is quite a bit cheaper (about 10% the price). That would allow you to practice a bit on the stainless, then once you are confident in your abilities, have a go at the Ti.

    - - - Updated - - -

    I will also add (having had a 7x lathe in the past), parting off large stock (anything over 1") is a nightmare. you may be better off pulling it out of the machine, and removing the partially machined part with a saw before putting it back in the machine and finishing it off. If you do the bore first, then parting off won't be as bad, because you will only be going through a thin section of material.
     
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  9. Caleb

    Caleb Iron Registered Member

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    That's a good idea. My plan is to finish the interior as much as possible before sanding/polishing, and then move to the exterior, then cut-off.

    I want to cut the stock into smaller pieces, but I feel like my chopsaw heats the material, and makes it harder to work with.
    Maybe I need to add bandsaw to my list down the line.

    It didn't even occur to me that I had the material too far from the tailstock, until my parting tool started wobbling under the pressure. I'm going to try to work as close to the stock as possible on the next piece. 1-2 diameter I think.

    Oh yeah, and I was using smaller bits to bore the hole, and boring bits to cut it to size. The titanium-carbide just wasn't cutting it. Going to order some cobalt ones tonight as Jim suggested.

    Thank you guys for your help.
     
  10. the2ndcashboy

    the2ndcashboy Swarf Registered Member

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    X2 on the work-hardening tendencies of Ti. I've never machined it but I have done a fair amount of drilling/grinding on titanium fasteners and sheet stock, and I can tell you rpm and feed rate are critical with Ti. It gets MUCH harder to work very quickly. If you're drilling holes, don't futz around, go ahead and do it. I don't have any experience with your lathe but I would agree with the previous poster that said 1/2" would probably be the limit for a drill, and even to do that I'd start at 1/8th or so and go up in fairly small increments.

    Also, you're probably aware that Ti is flammable, but it still needs to be said that it CAN catch fire (not easily, but it can happen especially if temps get high due to improper methods), and you WON'T be able to put it out until it burns itself out. Usually the risk of ignition is greater if you are making dust, but I've seen large shavings light off under enough heat/pressure.

    Edit: I also would recommend a good non-flammable cutting lubricant. I'm a fan of Boelube myself, but that's partially cause I get it free at work.
     
    Last edited: Sep 18, 2014
  11. bfd

    bfd United States H-M Supporter - Premium Content H-M Supporter-Premium

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    reminds me of an apprenticeship story we had a material at work called monel. made a nice ring so one apprentice was making a ring out of a monel bolt. bored the ring shaped the od and polished it to a bright finish. then parted it off . ring fell into chip pan. he picked it up put it on his finger. still very hot and a good burr on the inside. by the time he got it off his finger was bloody and a permanent burned ring was on his finger. called him Burnie after that. he didn't laugh go figure. bill
     
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